By breathless you mean you feel choking or that you don't recognise the breath? If it's the second one, no problem, just leave it as it is, it is a sign of calmness. If the first one, observe what changes, what makes you feel in need of air, try to breathe through the mouth.

"There is no such thing as the real mind. Ridding yourself of delusion: that's the real mind."(Sheng-yen: Getting the Buddha Mind, p 73)

Astus wrote:By breathless you mean you feel choking or that you don't recognise the breath? If it's the second one, no problem, just leave it as it is, it is a sign of calmness. If the first one, observe what changes, what makes you feel in need of air, try to breathe through the mouth.

Hi, its the second sensation. Not breathless before or after. Its almost as if I am exerting some sort of energy, a little like lifting a weight.

Then no need to worry about it or think to much of it. Of course, you may also make this situation a subject of your meditation, and look at it whether there is really a difference between breath and no breath.

"There is no such thing as the real mind. Ridding yourself of delusion: that's the real mind."(Sheng-yen: Getting the Buddha Mind, p 73)